Directional antenna



June 6, 1950 R. w. MASTERS 2,510,290

1 DIRECTIONAL ANTENNA Filed June 10, 1947 2 Sheets-Sheet l I INVENTOR. I ROBERT WAYNE MASTERS BY A 7 1% ".4

ATTORN EY J 950 R. w. MASTERS 2,510,290

DIRECTIONAL ANTENNA Filed June 10, 1947 2 Sheets-Sheet z r?" I l i 1 1 I a i I l I INVENTOR jiafiel'i Wgyzzeflhslers BY i 5 264 20:23-4 ATTORNEY Patented June 6, 1950 DIRECTIONAL ANTENNA Robert W. Masters, Erlton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application June 10, 1947, Serial No. 753,781

13 Claims. 1

The present invention relatesto directional antonnes and more particularly to directional ultra shortwave antennas. v

An object of the" present invention isto provide an antenna which permits wide control of the horizontal'radiatiofi pattern from one which is essentially circular to an essentially uni-directional pattern over a comparatively wide frequency range;

Another object of the present invention is the provisionof an antenna"v as aforesaid which may be installed'withou't usingf'pha'sing networks.

Another object ofthe: present invention is the provision-of a radiating unit which in itself a complete directionahantenna and whichmay'also constitute an-element ofan array;

A further obiect-of the present invention is the provision: of a-unit for a-multi-element directional antenna systemwhich-requires only one trans mission lineand end-sealwper bay of the" antenna.

Still another object of the present invention" is the provision of a slot-type antenna with supplementaryradiatorsconnected thereto 'for altering the radiationpattern-as required.

The foregoing objects-and others which may appear from the following'detailed: description are attained-by-providing an-antenna in-the form ducting rods arra'ng ed in layers s aced a'half' wavelength apart or they may be current sheet" radiators such as described in my prior filed appli cation, U. S;Serial 'No';:580}12U, filed February 28;

194-5, nowUI SzlPateiit 2;i80,155 issued August 30; 1-9459."

The present invention will be more fullyunderstood by'reference to the-followingdetailed description which is'a'ccompaiiied by drawing in which:

Figure 1 illustrates ineperspe'ctive an e'mbodi-' ment of thevpresent invention, while Figure 2 illustratesinperspective a modified form of-rthe present invention,

Figured-3 is;a=-familyofrcurves illustrating-various-d'irectivity patterns obtainable'with the structure shown in Figure 1,

Figure 4 illustrates in plan view a modification of the arrangement of'Figure' 2, and V )I Figure 5 illustrates in perspectivea' modification of the arrangement shown-inl' 'igure 1; a

Referring now toFiguresl and 2" there is a vertically disposed hollow conductive cylinder Hi having a longitudinal slot l2" extending from one end to the other. The extreme en'ds ofslot 52 are closed by conductive strips'ltl and M which may be either separate conductive strips bolted or otherwise secured into place or they" maybe integral portions of" the conductive cylindef l'fl-l The conductive cylinder is arranged to be'eouple'd' to suitable radiant energy transducermeans, such as a transmitter, by means'ofa transmission line TL. The transmission line" TL is preferably, but not necessarily, in the form of a coa xial'tran'smis'-' sion line having an 'out'er sheath l6 and an'inner conductor l8. Ihe outer-conductor it is electrically connected to the cylinder llla'lbhgfo'rl edge of slot 2 at a point approximately midwa'y along the length or slot 52. There; theinnerconduct'or' laex'tends across 'slo'til and connected to the opposite edge; In effect,- each' conductor of a two conductor transmission line isconnected to one edge of slot [2. The cylinder Hlas above described, is hown in Figure 2, as havinganum ber' of conducting rods 29, 2|, Zfand' 2-3 arranged in a single horizontal planeconnected tothe cyl-" inder' Eli and arranged to extend outwarmy from the surface of the cylinder. While I have shown the radiator rods 20- to 23 as extending radially away from the surf-ace of the cylinder in Fi'gs 1 and 2, a tangential arrangementasshown in'Figs;

4- and-E may under some-circumstances be used, especially if only a'single pairof radiating" rods used in each horizontal plane; When thus arranged magnetic coupling between currentsm the: cylinder and in" the radiator provides additional latitude'of adjustment for pattern control; The" rods mayha've a length of the order ofa quarter of the mean operating wavelength. My invention is", however, not limted to the'useof quarter ter'n control. However, the quarter 'wavelen'gth' rods have bee'n'joundtowork well, and, inmost cases,- to" provide sufficient radiating length -to' control the resultant pattern; As-ecorld 1ayer of radiating rods 30, 3|, 32 and 33 is similarly ar- 7 3 to the midpoint of the slot l2. That is, the rods 20, 2!, 22 and 23 are a quarter wavelength above the midpoint of slot l2 while rods 30 to 33 inclusive are a quarter wavelength below the mid way of slot l2. Such spacing results in a concentration of the radiation in the vertical plane.

Now, slotted cylinder in behaves as though there are very large standing waves of current and voltage about the peripheral surface. Thus, all voltages on the left side of the slot are opposite in polarity to those on the right half. The currents flow in the directions indicated by arrows 7:0 curving about the surface of reflector l2. In general, it will be found that, due to the short circuiting of slot l2 at the ends, the voltages across the slot are zero at the ends of cylinder Ill, increasing in magnitude as the center is approached. Since the voltage across slot I2 is balanced with respect to ground, there is a vertical line on the cylinder l opposite the lot at which the voltage is zero. The null line at the side of the cylinder opposite slot 12 is indicated by line 0. The radiators located near the null line opposite the slot or near the ends of slot l2 will not be driven very strongly due to the low voltage. On the other hand, the radiators located near a voltage maximum, for instance near the less extreme portions of the slot in the case of a cylinder a half wave in circumference,-will be driven strongly. Thus, a set of symmetrically located radiators such as those described with reference to Figure 2 may be driven with currents in the relationship indicated by the arrows z'r in the figure. The radiators to 23 and to 33 will radiate according to the magnitude and phase of the currents flowing in them. The separate layers, being symmetrically placed on the cylinder, will be energized in an in-phase relationship. The radiation pattern of the radially arranged rod radiators will combine with that of the vertical cylinder to obtain a radiation pattern shape which may readily be varied over very wide ranges.

If a wider band width is desired than that obtainable with the use of simple rod radiators, current sheet radiators such as described in my prior application, Serial No. 580,120, filed February 28, 1945, may be used. Such an arrangement is shown in Figure 1. The conductive cylinder and slot arrangement is the same as heretofore described, the only difference being the substitutionof sheet radiator elements 40, 4|, 42 and 43 for the rod radiators of Figure 2. Each sheet radiator element comprises a plurality of rod or tube members spaced from each other by a small fraction of a wavelength so that electrically each radiator acts as a continuous sheet and hereinafter the terms sheet, sheet radiator, "current sheet radiator are to be construed to include the last described type of radiator element as well as those of solid form. Preferably the edges of sheet radiators to 43 adjacent cylinder H] are straight or rectilinear, while the opposite edges are given a butterflywing formation. That is, the upper and lower edges are wider than the control portions of the sheet. Thus, as described in the above mentioned prior application, an improved directivity pattern is obtained in a vertical plane. Reference may be made to said application for a further analysis of the characteristics of the sheet radiators. The sheet radiators 40 to 43 inclusive are supported on cylinder H] by conductive brackets 45 at the upper and lower ends of the radiators. In addition to their supporting function, the brackets 45 also serve to electrically connect the sheet radiators to the conductive cylinder I0. Thus, when the conductive cylinder I0 is electrically grounded the entire radiating structure is protected against lightning strokes.

The current sheet radiators 40 to 43 inclusive are energized primarily from the induction field surrounding the conductive cylinder l0 rather than directly by voltages'existing on the surface of cylinder Ill since the supporting brackets 45 are connected to the cylinder ID at comparatively low voltage points. Experimental field patterns obtained with the arrangement of current sheets shown in Figure 1 indicate that the elements 40 to 43 were driven in such a manner as to cause reinforcement of the field of the cylinder in a direction radially from the slot and cancellation in the opposite direction. Measurements made on an antenna arrangement such as that shown in Figure 1 indicate that the antenna is sufficiently broad band for use in television broadcasting. It is also highly effective for use as a frequency modulation broadcasting antenna. As intimated hereinbefore, the current sheet radiators need not be radially arranged with respect to the cylinder in but may be inclined at an angle thereto as shown in Fig. 5. Especially where but two such radiators are employed, an additional adjustment is obtained in the variation of the angle which the plane of the current sheet radiator makes with the plane passing radially through the-center of cylinder Ill, which adjustment may be found useful in obtaining the desired field pattern,

Figure 3 shows measured field patterns obtainable with the antenna of Figure 1 as the frequency applied thereto is varied. The current sheet radiators 40 and 30 were of a size suitable for resonance at about 60 mc. while the cylinder l0 and slot l2 were adjusted for resonance at about 82 mo. The cylinder in the embodiment tested was 23 inches in diameter. Curve 6B shows the radiation pattern shape obtained when the antenna of Figure 1 was energized at 67 mo. while curve 62 shows the radiation pattern at mo. and curve 64 shows the radiation pattern at me. These curves are of course referred to the horizontal plane with the slot l2 of the radiator of Figure 1 placed at the zero point of the ordinates with the slot facing in the plus direction.

While I have illustrated a particular embodiment of the present invention, it should be clearly understood that it is not limited thereto since many modifications may be made in the several elements employed and in their arrangement and without departing from the spirit and scope of the invention.

, What is claimed is:

1. An antenna including a hollow conductive cylinder having a narrow longitudinal slot along the length thereof, means for coupling a transmission line directly across said slot, and a number of radiators arranged on and extending outwardly from the outer surface of said cylinder in a plane transverse to the axis thereof, said radiators being positioned about the periphery of said cylinder to obtain a, predetermined directivity pattern.

2. An antenna including a hollow conductive cylinder having a circumference substantially equal to a half of the operating wavelength and a length of substantially one wavelength and having a longitudinal slot along the length thereof, means for coupling a transmission line directly across said slot, and a number of radiators radially arranged on and extending outwardly from the outer surface of said cylinder, said radiators being positionedaabout'the periphery of said cylinder :to obtain a predetermined directivity pattern.

BJ-mr antenna "including a hollow conductive cylinder having a circumference substantially equal to a half-of the operating wavelength and a length of substantially. one wavelength,and having a longitudinal slot along the :lengthof said cylinder, means for coupling a high frequency transducer directly across said slot, and a number of radiators arranged on and outwardly extending from-the outer snrfacesiof said cylinder} said radiatorssbeing positioned .about the periphery of said cylinderto obtain a predetermined directivity pattern.

An antenna including .a hollow conductive cylinder having .a circumference substantially equal to a half of the operating wavelength and alength-of substantially one wavelength andshavingaa longitudinallslo't along the .length of said cylinder, means ifomcoupling a transmission .line across said slot, and a number of radiators radially arranged at current maxima at the outer surface of said cylinder, said radiators being positioned about the periphery of said cylinder to obtain a predetermined directivity pattern, said radiators being in the form of, spaced outwardly extending radiator elements having at least one end thereof connected to a substantially rectilinear conductor arranged parallel to the surface of said cylinder, and conductive supporting brackets at the upper and lower ends of said rectilinear conductors electrically connecting said radiators to said cylinder.

5. An antenna including a hollow conductive cylinder having a circumference substantially equal to a half of the operating wavelength and a length of, substantially one wavelength and having a longitudinal slot along the length of said cylinder, means for coupling a transmission line across said slot, and a number of radiators radially arranged at predetermined points on the outer surface of said cylinder, said radiators being positioned about the periphery of said cylinder to obtain a predetermined directivity pattern, said radiators being in the form of vertically spaced outwardly extending horizontal radiator elements having at least one end thereof connected to a substantially rectilinear conductor arranged parallel to the surface of said cylinder, and conductive supporting brackets at the upper and lower ends of said rectilinear conductors electrically connecting said radiators to said cylinder.

6. An antenna including a hollow conductive cylinder having a narrow longitudinal slot along the length thereof, means for coupling high frequency transducer means directly across said slot, and a number of radiatorsradially arranged on and extending from the outer surface of, said cylinder in a plane transverse to the axis thereof, said radiators being positioned about the periphery of said cylinder to obtain a predetermined directivity pattern,

7 An antenna including a hollow conductive cylinder having a circumference substantially equal to a half of the operating wavelength and a length of substantially one wavelength and having a longitudinal slot along the length of said cylinder, means for coupling a two conductor transmission line directly across said slot near its midpoint, and a number of radiators radially arranged on and extending from the outer surface of said cylinder, said radiators being positioned about the periphery of said cylinder to obtain a predetermined directivity pattern.

8. An antenna including a hollow conductive cylinder having -.acircumference substantially equal :toa half of theoperating wavelength and aslength of substantially onewavelength andhaving'a longitudinal .slot along the length of said cylinder,- means for'coupling a two conductor transmissionirline directlyacross said slot near itssmidpoint, and-a number of radiators arranged in outwardly-extending relationship on the outer surfaceof-said cylinder, said radiators being positioned about theperiphery of-said cylinder to obtain apred'etermined directivity pattern.

\9. 'An antenna including a hollow conductive cylinder :having a circumference substantially equalto a half of the operating wavelength and alength-of substantially one wavelength and .havingaa longitudinal slot along the length of said cylinder,-.-a*two conductor transmission line across said-slot having oneconductor connected to each edgeof-said slot at substantially its midpoint, and a number :of radially arranged radiators at the outer surface ofsaid cylinder, said radiators being positioned about the periphery of said cylinder to obtain a predetermined directivity pattern, said radiators being in the form of outward- 1y extending rodlike radiator elements spaced apart in the direction of the axis of said cylinder and having one end thereof connected to substantially rectilinear conductor arranged parallel to the surface of said cylinder, and conductive supporting brackets at the upper and lower ends of said rectilinear conductors electrically connecting said radiators to said cylinder.

10. An antenna including a hollow conductive cylinder having a circumference substantially equal to a half of the operating wavelength and a length of substantially one wavelength and having a longitudinal slot along the length of said cylinder, a two conductor transmission line across said slot having one conductor connected to each edge of said slot at substantially its midpoint, and a number of radially arranged radiators at the outer surface of said cylinder, said radiators being positioned about the periphery of said cylinder to obtain a predetermined directivity pattern, said radiators being in the form of quarter wave rods connected at one end to the surface of said cylinder.

11. An antenna including a hollow conductive cylinder having a circumference substantially equal to a half of the operating wavelength and a length of substantially one wavelength and having a longitudinal slot along the length of said cylinder, a two conductor transmission line across said slot having one conductor connected at each edge of said slot at substantially its midpoint, and a number of radially arranged radiators at the outer surface of said cylinder, said radiators being positioned about the periphery of said cylinder to obtain a predetermined directivity pattern, said radiators being in the form of quarter wave rods connected at one end to the surface of said cylinder, said rods being arranged symmetrically in horizontal planes spaced a distance substantially equal to a quarter wavelength above and below the horizontal plane passing through said midpoint.

12. An antenna comprising a hollow conductive cylinder having a narrow longitudinal slot along the length thereof and means for coupling a transmission line across said slot to produce an induction field surrounding said cylinder, a plurality of outwardly extending radiator elements spaced in the direction of said slot and having one end thereof connected to a substantially rectilinear conductor arranged parallel to the surface of said cylinder and electrically coupled to said cylinder at the upper and lower ends of said rectilinear conductors, said elements being energized by said induction field to obtain a predetermined directive radiation pattern.

13. An antenna comprising a hollow conductive, cylinder havin a narrow longitudinal slot along the length thereof and means for coupling a transmission line across said slot to produce an induction field surrounding said cylinder, a plurality of outwardly extending radiator elements each connected at one end to a substantially rectilinear conductor arranged parallel to the surface of said cylinder, said elements being spaced apart in the direction of the axis of said cylinder, and conductive supporting brackets electrically connecting the upper and lower ends of said rectilinear conductors to said cylinder at current maxima positions about the periphery of said cylinder, said elements being energized by said induction 8 field to produce a predetermined directive radiation pattern.

ROBERT W. MASTERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Characteristics of the Pylon F. M. Antenna, by R. I-Iolz, published in F. M. and Television,

, September 1946, pages 45 and 46. 

